1. Field of the Invention
The present invention relates to the field of transgenic plants. More particularly, the present invention relates to transgenic plants exhibiting modified flower color.
2. Description of Related Art
Horticultural and ornamental markets are driven by innovation in color, shape and other esthetic parameters of the ornamental plants. New colors of roses and carnations, new shapes and colors of flowers find their way to the marketplace every year and the outdated varieties are replaced by new ones. Generation of new and esthetically pleasing varieties is known to be the key force driving the floriculture industry and allowing its growth.
Iris is a winter hardy, herbaceous perennial consisting of approximately 300 species, many of which are popular ornamentals in the temperate regions of the Northern Hemisphere. While being amongst the most horticulturally important species, and having variety of flower colors including yellow, blue, and burgundy, there are currently no iris species with truly red flower color.
Iris flowers have almost no red pigment naturally, and irises currently commercialized as “red” are actually shades of wine, brick, or reddish brown. Two types of pigments contained within iris plant cells, e.g., oil-soluble xanthophylls and carotenoids that produce yellows, pinks, and oranges in flowers, and water-soluble anthocyanins that produce blues and purples, mix in the epidermal layer, resulting in a combination of pigments perceived by the eye as reddish.
Iris germanica is one of the most popular iris species. Flower color in I. germanica is determined by two distinct biochemical pathways, the carotenoid pathway creates yellow, orange, and pink flowers, while the anthocyanin pathway produces blue and purple flowers. Similarly to the other members of the iris genus, there are no truly red I. germanica flowers. Conventional breeding methods have so far failed to generate them due to lack of genes capable of generating truly red pigment within the iris gene pool.
U.S. Pat. No. 5,880,332 discloses the nucleotide sequence of the capsanthin-capsorubin synthase (ccs) gene from pepper (C. annum), which catalyzes the biosynthesis of the red carotenoids capsanthin and capsorubin, and does not suggest the newly discovered ccs sequence of lily (L. lancifolium) disclosed herein, there being less than 60% sequence homology between the genes. Notably, the lack of significant relationship between the lily and pepper ccs prevented identification of the lily gene using heterologous non-degenerate primers based on the pepper sequence (Jeknic et al. (2012) Plant & Cell Physiol. 53(11): 1899-1912). As such, U.S. Pat. No. 5,880,332 does not disclose or suggest L. lancifolium ccs, transgenic iris plants containing a ccs gene, or red, or red/orange, irises.
U.S. Pat. No. 6,459,017 discloses methods for transformation and regeneration of transgenic iris plants; however, this patent does not disclose or suggest capsanthin-capsorubin synthase for such transformation, and does not disclose the ccs sequence of lily (L. lancifolium), or red, or red/orange, irises.
A truly red bearded iris, like a truly blue rose, has remained an unattained goal for decades despite frequent hybridizing and selection. There are species and selections, most notably based on the beardless rhizomatous Copper iris (I. fulva), that have a relatively pure red color. However, introducing this color into a modern bearded iris breed has proven very difficult, and the vast majority of irises are in the purple and blue to blue violet color range, with yellow, pink, orange, and white breeds available.
It would therefore be useful to introduce new genes enabling generation of truly red pigment in the iris genus, beyond what is available in the native iris genome. New varieties of red or red/orange color in iris will produce a long-awaited increase in the assortment and variety of these ornamental plants available to the consumer.
The present invention addresses the need in the art for iris plants with truly red, and red/orange, pigment in their flowers. The methods disclosed herein enable the production of new varieties of red and red/orange colored iris flowers, containing capsanthin and/or capsorubin, satisfying consumer desire for an increase in the assortment and variety of these commercially important ornamental plants.